Yagi pointed to which repeater?

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cratliff

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I am looking to build a yagi tuned to 855mhz to use to experiment around with. I live in NE Phoenix area and am able to pretty decently pick up a lot of action i.e. sherriff, jails, and probation coming off of the Thompson Peak repeater. First, I cant seem to locate the exact location of the repeater. I only generally know where the Thompson Peak area is. Secondly, when using a yagi do you want to direct it toward an already decently strong signal or aim for a repeater that is farther away and getting more faint reception?

On a similar topic but a also as a sidenote, if I tune a yagi to the airband and point it to Sky Harbor Airport, with Camelback mountain in the way (mountain is 10 miles from me, airport is 15-20 miles) would a yagi be able to bring in more coming from the Airport?

I am pretty new to REALLY scanning in the Phoenix area and new to antennas also. I have been reading all over these forums and elsewhere trying to learn as much as I can, so I hope these questions don't seem redundant.
 

AZScanner

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I would recommend pointing it toward the weaker signal. Pointing it towards a signal that you are already receiving well might actually make reception worse than before by overloading the receiver.

As for an airband yagi pointed at camelback, you can certainly give it a try, it might help. However an airband yagi will be quite a different animal that one tuned for 855MHz. You certainly wouldn't be able to just point your 800MHz yagi at Sky Harbor and pull in good reception on the airband (but, if you have a digital scanner you can probably pull in the DTRS site there :twisted:)

If monitoring Sky Harbor is what you're after (and you've got a broadband connection) I suggest this site: http://www.liveatc.net/feedindex.php - scroll down or search for "KPHX". Perfect reception of Sky Harbor from anywhere in the world! :) Squawkvfr.net also has a feed, but it's down at the moment.

Wish someone (ahem ABC15) would point a webcam at the airport and stream video to go with the audio feed. That'd rock. I'd watch that all day.

-AZ
 

k8tmk

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Cratliff:

Yagis by nature are directional antennas that provide gain (ie: improve signal strength) in the direction they are pointed. Having said that, you want to point the yagi at the station (tower) you want to hear. Pointing it toward am already-strong signal will not help you with a weaker repeater, unless they happen to be in line (same direction) from your location. If you aim the yagi at the weaker station, and they are in different directions, chances are the previously stronger station will become weaker.

As for pointing the yagi at the airport, it may or may not help. Higher frequencies tend to be line-of-site. As such, they are adversely affected by objects in the way.

Hope all of this helps.

Randy
 
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It depends on what you are having trouble hearing and want to hear better. The most interesting stuff IMHO is on the Phoenix simulcast A, which is where Phoenix PD can be found. A close runner up would be Glendale Police, followed by Scottsdale PD which does almost everything "in the clear". Can you give me cross-streets for your location? I would bet if you are in NE Phoenix your nearest simulcast site is at 15040 N. Tatum if I remember correctly. Just south of Greenway in other words. But you need to take a look at the list of sites for simulcast A, and try to point the yagi in such a way that only one site has gain and the others have attenuation, so that you can hear everything without cut-outs. This might mean you are NOT aiming at the nearest site. You need to plot out your location, as well as all sites within ten miles, then see how you can aim the yagi as I already have described. So that only ONE site hits your scanner hard and the others are attenuated. With the yagi on a mast above the roofline, you should clearly be able to copy a site from ten miles unless there is something major in the way.

I use this system and monitoring of simulcast a is quite good now. What really blows me away is that ALL 800 mhz signals from ALL directions come in very well, so you don't have to worry about blocking anything out. You are just trying to get a good ratio of gain to attenuation on simulcast a when comparing your target tower to the other nearby towers. My wilson yagi even does amazingly well on the VHF high airband, although stragely it doesn't do as well on VHF High 154 mhz where the FD is at, although it is still good enough to hear the dispatcher clearly except when the broadcast is from South Mountain. 440-470 uhf works ok as well, so you will still enjoy those things.

In fact, if you aren't that interested in distant VHF and UHF signals, the 800 mhz yagi could well be all that you need. My antenna switch is set to the yagi nine times out of ten these days, only switching to the ground plane antenna to pick up weak vhf stuff occasionaly

If all of this seems a bit confusing, post your cross streets and I will be happy to suggest which way I would aim the yagi from your location.

MCSO is going to come in fine whichever way you aim anyway since you won't be far from Thomson Peak which is about 11000 east, just north of where Bell Road would be if it ran that far, and since that is a pretty tall peak, you are going to get great signal no matter what. I don't monitor the airport stuff so I can't really advise on that one.
 

cratliff

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Hello and thank you for all the input! My cross streets are 1/2 mile north of Bell Road and Tatum so i am really close to the tower at Greenway and Tatum. I never knew that is what that tower was for! I have been listening to the Simulcast A for a while tonight and it comes in 100% no problems with reception and no noise at all, all with a little indoor antenna! I asked about Thompson Peak because I pick a lot of things up pretty well from there as well as White Tanks (Mostly MCSO and jails like I mentioned before). I dont know about building that yagi anymore. Apparently I live so close to 2 towers that I dont really need one? My goal in building one was to: 1. Do it myself 2. Learn about antennas in the process 3. Pick up signals from farther away and hear more activity. Any advice there?

I am most interested in the public service bands (I am majoring in Criminology in school and planning on a law enforcement career) and airbands (I have taken flying lessons and love airplanes). I picked up a Maldol AL-500H to use with my Pro-95 and I can hear tower and aircraft activity from Scottsdale, ATIS and pattern activity from Deer Valley, A little hit now and then from Glendale, and lots of things from Sky Harbor. I had hoped that maybe a directional antenna would help me wheel in the tower transmissions from KPHX though.

So I guess my question now would be this: I dont know what I will be able to construct as far as an outdoor antenna, I want to listen to things as far away as I can manage (cause it's more fun that way of course), and I have a couple of pretty nice scanners to work with, what would all you EXPERTS :) have to give in the way of advice. I have read the antenna and scanning forums to death, read all kinds of articles, catalogs and websites and still dont really know what my best options are. And being a college student, I dont have ton to spend (another reason I like to build things myself).

Sorry for the long winded reply!!
 
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Well you are one lucky guy being that close to the northeast most tower, and having no other site really that close to you. You SHOULD be getting perfect reception so close to one tower and so far from the others. I am jealous. I wish my handheld scanner could receive perfectly on simulcast a but am right between two sites so it is horrible and good reception only comes from the yagi / base scanner.

You are so close to Thomson Peak as you mentioned that you don't need any yagi for the Maricopa County system.

You didn't mention Glendale PD so I don't know how that comes in for you. If it comes in badly or not at all a yagi would be worth building for that alone. They are a great PD to monitor with plenty of action, as well as interesting (at least I think) surveillance stuff mostly in the clear. Their detectives are very active. You might even be able to angle the yagi enough to get Buckeye and Goodyear also. Nothing really exciting there usually, but it adds a few agencies to you scanlist. You are so close to the MCSO and Phoenix sites that it won't matter how the yagi is pointed, they will come in crystal clear.

As far as airband it seems a yagi would be a pain to build for that low of a frequency, but I am not saying it can't be done.

I would suggest (if you can swing it) a 1/4 ground plane antenna with the center element cut for 118 mhz or so. You can order custom cut ground planes off the web for maybe $30, and mast and some good cable might run you $70 total, so maybe if you can swing $100 at some point you could really be set up for good airband reception. I just use the radioshack 20-176 and it works pretty well for airband, even though the element is cut for 155 mhz I believe (too short for optimal airband reception).

For a few dollars more though you could just order an airband ground plane, and it would work fine for VHF public safety too. This is something I am considering doing right now actually. The thing I like about airband is that the most interesting conversations (to me) are the ones that take place between all the valley helicopter pilots, especially the PD pilots. They talk on 123.5 and 123.025 mostly although there are a few others to watch. These guys talk very openly on these frequencies and it is a great way to get details on things happening where the guys on the main PD frequencies are going to be much more discreet about what they say.
 
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cratliff

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Phoenix, AZ
I have never checked out Glendale PD for any period of time to really hear much of what is going on. I will have to check that out, Scottsdale PD as well. I have had 123.025 in my Pro-95 for a while and never heard all that much talk that was interesting there. I plugged in 123.5 and 123.05 so maybe between the three I'll be able to get something good. Phoenix has a pretty decent fleet of PD helos (7 I believe) so there should be some action.
As for a yagi, that idea may be something I build for the fun of it if anything and I can just aim it around a little to experiment.
A 1/4 inch ground plane would be something fun to check out for sure. In this situation I almost wish I lived farther away just so I'd have something to work for!
 
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